The present disclosure relates to the charge of an electric vehicle.
Electric vehicles mean vehicles operating by using electricity and may be roughly divided into a battery-powered electric vehicle (EV) and a hybrid electric vehicle (HEV). The battery-powered EV is a vehicle running by using only electricity without using fossil fuel and is generally named as an EV. In addition, the HEV means a vehicle running by using electricity and fossil fuel. In addition, the EV includes a battery supplying electricity for running. In particular, the battery-powered EV and a plug-in type HEV uses power supplied from an external power supply to charge a battery and uses power charged in the battery to operate an electric motor.
In general, a relay is being used in order to control power supply from a high-voltage battery pack to a motor.
For example, the EV or the hybrid vehicle includes the relay installed between the battery pack and a high-voltage circuit part in order to control power supply from the high-voltage battery pack to the high-voltage circuit part. In addition, the connection or disconnection between the high-voltage circuit part and the battery pack is performed by the relay according to a vehicle control state.
In this example, the reason why the relay is used is to ensure electric complete insulation between an energy storage medium and other systems, in which case electric stability is ensured because the relay is shorted and power is supplied when a vehicle is in operation, and the relay is open in a key off, maintenance or emergency state. Also, when a first accident occurs, an electric shock resulting from a high voltage or a second accident that is serious, such as fire is prevented, and dark current from the battery pack is blocked.
Therefore, when the relay has welding due to an over-current, an abnormal current flows in a battery system and thus a dangerous situation occurs.
As an example, in the case of the hybrid vehicle, the back electromotive force of a motor is generated according to engine RPM when a motor controller goes wrong, so a situation in which a battery is over-charged occurs. In this case, when the battery is over-charged, a battery control unit opens the relay in order to protect the battery but when the relay is welded for other reasons despite an open command by the control unit, there is a possibility that fires occurs or a vehicle explodes due to continuous over-charge.
Thus, it is important for safety to detect whether there is welding on relays connected to the battery pack in battery systems for various electric vehicles HEV, PHEV, and EV or an energy storage system (ESS).